3c933b96e0
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The unattended window's W1/W2. Both routers now carry the VLAN 2 IPv6 config (addresses ::1/::2, RA with managed-flag + no-autonomous-flag + link-mtu 1472, DHCPv6 reservations for all five nodes), applied via migration/vlan2-v6-apply with a vlan2-v6-watchdog armed on both routers throughout. IPv4 untouched: internet up, 6 MASTER / 6 BACKUP, 5/5 nodes Ready, watchdogs quiet. default-lifetime 0 on purpose -- addressing without egress. Turning on v6 egress moves image pulls onto a tunnel of unmeasured throughput, and the person who would notice is away. One line to flip when attended. THE WINDOW'S QUESTION IS ANSWERED, HALF YES, HALF NO: YES: NetworkManager follows the managed flag. worker0 logged dhcp6 (eno1): activation: beginning transaction minutes after the RA appeared. "ipv6.method=auto will do DHCPv6" is now evidence, not inference. NO: the reservations never match. Every packet kea logs is [no hwaddr info] -- the clients identify with DUID-UUID (and one DUID-LLT), kea derives no MAC from any of them, so hw-address reservations cannot match and no node got its reserved address. VyOS accepting `static-mapping mac` renders valid kea config that simply never matches these clients. The "one source of truth with IPv4" addressing scheme does not survive contact with DHCPv6; options (DUID keys, kea mac-sources, dynamic range + discovery, or SLAAC) are written up in migration/window-evidence/2026-09-06-dhcpv6.txt for an attended decision. FOUND LIVE AND FIXED IN THE SAME WINDOW: `service dhcpv6-server` with no listen-interface renders kea6 with interfaces: ["*"] -- a DHCPv6 server on EVERY VLAN. kea was answering an unrelated device on bond0.10 within seconds of the first apply. Same family as the kea IPv4 cross-VLAN bug (ISC #1117). Now pinned to bond0.2 on both routers. Also in this commit, three self-inflicted script bugs found by their own failures: log() wrote progress lines into the captured config stream (VyOS rejected each as "Invalid command", leaving the two routers correct but NOT identical); "Invalid command" was missing from the failure patterns so that run reported success; and the MAC lookup matched its own freshly-created v6 reservations on the second run, returning doubled MACs. All three fixed, both routers converged and diffed identical. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01DMVzWZgiKW2wquf5z8S1yH
57 lines
3.2 KiB
Plaintext
57 lines
3.2 KiB
Plaintext
=== W2: does a production node take a DHCPv6 reservation? ===
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Window of 2026-09-06, operator offline.
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SHORT ANSWER: the RA half works; the RESERVATION half does not, and the reason
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is structural rather than a misconfiguration.
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WHAT WORKS
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- RA is emitted on bond0.2 with AdvManagedFlag on, AdvAutonomous off,
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AdvLinkMTU 1472, AdvDefaultLifetime 0 (deliberately not a default router).
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- NetworkManager on worker0 SAW it and acted:
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dhcp6 (eno1): activation: beginning transaction (timeout in 45 seconds)
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So "ipv6.method=auto follows the managed flag" is now EVIDENCE, not
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inference. That was the open question this window set out to close.
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- kea-dhcp6 runs on both routers and receives SOLICITs on bond0.2.
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WHAT DOES NOT WORK, AND WHY
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Every DHCPv6 packet kea logs is annotated [no hwaddr info]:
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duid=[00:04:69:d9:30:64:c3:4e:...] [no hwaddr info] <- DUID-UUID (type 4)
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duid=[00:04:25:11:e0:0a:7b:c4:...] [no hwaddr info] <- DUID-UUID
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duid=[00:01:00:01:31:78:0a:ae:...] [no hwaddr info] <- DUID-LLT (type 1)
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DHCPv6 identifies a client by DUID, not by MAC. kea can sometimes DERIVE a MAC
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(its mac-sources machinery), but here it derives nothing -- including from a
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DUID-LLT, which does embed one. So `hw-address` reservations cannot match, and
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a node that solicits gets no reserved address.
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VyOS accepting `static-mapping <name> mac` is therefore necessary but NOT
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sufficient: it renders valid kea config ("hw-address": "78:55:36:08:28:fb",
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confirmed in /run/kea/kea-dhcp6.conf) that simply never matches these clients.
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The plan's assumption -- "reservations keyed on MAC, one source of truth with
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IPv4" -- does not survive contact with DHCPv6.
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OPTIONS, none free, for an attended session:
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a) Key reservations on DUID (VyOS static-mapping supports `duid`). Works, but a
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DUID is client-generated: it is a SECOND source of truth, it must be
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harvested per node, and it changes if a node is rebuilt -- which is exactly
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the "out of the box for new nodes" property we were trying to preserve.
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b) Set kea `mac-sources` explicitly and see whether any method recovers a MAC
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from these clients. Cheap to try; may simply not work for DUID-UUID.
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c) Drop reservations: hand out a dynamic range and have labctl DISCOVER the
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node's address rather than predict it. The k3s preflight (914135c) already
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refuses to write a node-ip the node does not hold, so discovery is safe --
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but the address is then not knowable before the node boots.
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d) SLAAC with no-autonomous cleared, and accept EUI-64 addresses. Stable per
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NIC and needs no server state at all, but the address is not ours to choose.
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A SECOND FINDING, unrelated and worse if unnoticed
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`service dhcpv6-server` with no listen-interface renders kea6 with
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interfaces: [ "*" ] -- a DHCPv6 server on EVERY VLAN. Observed live: kea began
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answering SOLICIT/REQUEST from an unrelated device on bond0.10 (LoT) within
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seconds of the first apply. Same family as the kea IPv4 cross-VLAN bug (ISC
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#1117) this estate already fought. Fixed by pinning
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`set service dhcpv6-server listen-interface bond0.2` plus a subnet-level
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`interface bond0.2`; both routers now render interfaces: ["bond0.2"].
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